CO2 Diffusion - The Planted Tank Forum
 
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post #1 of 9 (permalink) Old 07-07-2015, 06:34 PM Thread Starter
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CO2 Diffusion

Quick question-

I made a DIY CO2 generator, and I'm wondering if an airline connecting to a powerhead output is enough to diffuse the CO2. Video for reference:

https://www.youtube.com/watch?v=AshH9Tt0-UE

I'm getting so much pressure because the CO2 generator has an airline in one of the bottles. (Unproven, but I'm hoping the agitation and oxygenation causes the yeast to go into overdrive)

The one of the left has the airline going into it:


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post #2 of 9 (permalink) Old 07-07-2015, 09:44 PM
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Don't use an airline in a DIY yeast CO2 bottle! The airline will just add a lot of air to the small amount of CO2 you are injecting into the water. It does nothing of value.

You can diffuse the CO2 by sticking the end of the CO2 line into the inlet of a little powerhead or other tiny pump, but it works better if you use something to break up the big CO2 bubbles into microscopic bubbles first. A lot of people have had success with using a small piece of bamboo chopstick in the end of the CO2 tube. I used a small air stone that way and it worked well too.

Hoppy
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post #3 of 9 (permalink) Old 07-08-2015, 04:18 AM Thread Starter
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The oxygen doesn't enable aerobic respiration in the yeast?


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post #4 of 9 (permalink) Old 07-08-2015, 09:43 PM Thread Starter
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Oxygenating the yeast works too well, even for a 50 gallon tank. My shrimp were at the surface gasping. I turned the O2 off. Now the CO2 is coming out at a nice trickle.


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post #5 of 9 (permalink) Old 07-08-2015, 11:40 PM
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Usually when people do DIY CO2 things are forgotten.
When too much alcohol is produced (around 12%) yeast will no longer work.
Remedy is too add more water and yeast at the same time.
Twice the life from one serving of sugar that is still there.
Just a thought.

As for delivery of CO2 I would choose nothing less than a reactor
on the discharge of a canister filter.
When first charging a bottle sure I waste a little but in a 40G I can always easily achieve 45-65ppm with no effort.
I have been forced at times to add an airstone as to not gas fish.

A note.on this, sometimes additional yeast and water can even be added twice.


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Growing is not that difficult.
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post #6 of 9 (permalink) Old 07-09-2015, 08:45 AM
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Quote:
Originally Posted by MassiveDynamic17 View Post
Oxygenating the yeast works too well, even for a 50 gallon tank. My shrimp were at the surface gasping. I turned the O2 off. Now the CO2 is coming out at a nice trickle.
The extra CO2 with the air stone is not really because the yeast is being oxygenated. Oxygen from air bubbles doesnt dissolve in water that easily. The extra CO2 is from the turbulence created by the air bubbles rising. Similar to what happens if you shake a reactor bottle. You'll get a blast of co2 until it settles down again.

It is an interesting effect, but it's just going to expire the mixture faster.


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post #7 of 9 (permalink) Old 07-12-2015, 04:39 AM
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I'm gonna glom on to this one since it's titled diffusion.

I've only just begun making CO2 for the tank, but have been brewing for years. Generating the CO2 is not an issue. Diffusing it, however...

What I've done today is drill a hole it the bottom of the HOB intake pipe and inserted the discharge end of the CO2 hose into it. As the HOB draws up water, it carries the CO2 with it. The impeller in the HOB chops up the CO2 bubbles, dumps them and the water into the filter box, the CO2 laden water passes through and over the filters, and spills over into the tank. Sounds good. What do y'all think?

I do imagine some of the CO2 escapes in the short waterfall.

Since the HOB is more of a water lifter, and not a centrifugal pump, I'm not worried about entrained gas causing cavitation and the problems that come with that, but I can hear when bubbles pass through the impeller chamber. They be gettin chopped, yo. Has anyone done this and worn out the impeller or motor prematurely?
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post #8 of 9 (permalink) Old 07-12-2015, 05:33 AM
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Quote:
Originally Posted by Bine View Post
I'm gonna glom on to this one since it's titled diffusion.

I've only just begun making CO2 for the tank, but have been brewing for years. Generating the CO2 is not an issue. Diffusing it, however...

What I've done today is drill a hole it the bottom of the HOB intake pipe and inserted the discharge end of the CO2 hose into it. As the HOB draws up water, it carries the CO2 with it. The impeller in the HOB chops up the CO2 bubbles, dumps them and the water into the filter box, the CO2 laden water passes through and over the filters, and spills over into the tank. Sounds good. What do y'all think?

I do imagine some of the CO2 escapes in the short waterfall.

Since the HOB is more of a water lifter, and not a centrifugal pump, I'm not worried about entrained gas causing cavitation and the problems that come with that, but I can hear when bubbles pass through the impeller chamber. They be gettin chopped, yo. Has anyone done this and worn out the impeller or motor prematurely?
It wont wear out the impeller, but the chop sound can be quite annoying. It'll work better (and be silent) if you pre-diffuse it with a piece of cotton ball or chopstick in the end of the co2 line. That way the filter is working against a bunch of tiny bubbles instead of one big one.

Check out the right hand link in my sig for an in depth discussion on using HOB filter for diffusion.


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post #9 of 9 (permalink) Old 07-12-2015, 06:06 AM
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Quote:
Originally Posted by burr740 View Post
It wont wear out the impeller, but the chop sound can be quite annoying. It'll work better (and be silent) if you pre-diffuse it with a piece of cotton ball or chopstick in the end of the co2 line. That way the filter is working against a bunch of tiny bubbles instead of one big one.

Check out the right hand link in my sig for an in depth discussion on using HOB filter for diffusion.
Nice! Fine diffusion before the impeller.

Grrrssshh! Grrrssshh! It's doing it now.
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